1. Field of the Invention
This invention relates to a process for preparing a coal derivative comprising a mixture of monocyclic, polycyclic, multifunctional carboxylic acids which comprises contacting coal with aqueous nitric acid and then drying the resulting product to remove water therefrom. Preferably the process involves contacting a portion of the coal to be treated with aqueous nitric acid and then adding the remainder of the coal to the reaction mixture prior to the end of the reaction period.
2. Description of Prior Art
In U.S. Pat. No. 4,052,448 of Schulz et al, dated Oct. 4, 1977, there is disclosed a process for preparing coal derivatives which comprises subjecting a slurry containing coal to reaction with aqueous nitric acid, mechanically separating the solids in the resulting slurry to obtain a mixture of water-insoluble coal derivatives and a mixture of water-soluble coal derivatives. The water-insoluble coal derivatives are then separated into a solvent-soluble, water-insoluble fraction and a solvent-insoluble, water-insoluble fraction. In the specific examples therein the reaction product is subjected to filtration to separate the water-insoluble coal derivatives therefrom. Unfortunately, such filtration, or other mechanical separation that is contemplated therein, is cumbersome, time consuming and expensive.